Hi all, just bought a 1987 truck extra cab, trying to do all the maintenance, and was reading the manual, it said GL4 (75w-90) OR GL5 (80W-90), which one should I use and why? there seem to be lots of different opinions. thanks guys

 

Which manual? Which component?

 

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Congrats on your new ride... the teaser pic looks like a very slick ride... more pics please.
info on your rig will be very helpful in the future, the more the better.
welcome to yotatech.

 

Use GL-5 in the differentials, and GL-4 in the transfer case and manual gear boxes.
Cheers